I’m writing a character’s description, and I’m stuck on my hero’s “greatest strength”. He is very routine, and organized (which manifests more as he’s responsible and less as stubborn inflexibility). The word also need to have a positive connotation of course, and need to imply he goes through with promised commitments- his yes means yes and his no means no.
In a positive sense, somebody who always does the same thing (especially in the case of honouring their commitments) is somebody who is reliable:
1 : suitable or fit to be relied on : DEPENDABLE
2 : giving the same result on successive trials
In other words, you could say the following about him:
He's reliable. I can trust that he will be organized, be there on time, and do what he says.
Of course, some people also use the word reliable when talking about somebody's negative qualities (you can rely on him to make a mistake), but it's said in a sarcastic sense, one that twists the normal meaning. It has the same contradiction as you can trust him to lie.